Polyamide acid resins and polyimides therefrom



United States Patent 3,435,002 POLYAMIDE ACID RESINS AND POLYIMIDES THEREFROM Fred F. Holub, Scotia, N.Y., assignor to General Electric Company, a corporation of New York No Drawing. Filed May 15, 1967, Ser. No. 638,636 Int. "C1. C08 20/20, 20/32 U.S. Cl. 260-465 7 Claims ABSTRACT OF THE DISCLOSURE Esters or amides of trimellitic anhydride can be prepared by reacting the latter with either a polyol or a disecondary amine at elevated temperatures and by a rearrangement reaction involving the elimination of water to obtain the ester or amide polyanhydride. Polyamide acid resins and polyamides can be prepared from such compositions.

This invention is concerned with a process for preparing esters (which term is intended to include thioesters) and amides of trimellitic anhydride, and the making of polyamide acid resins and polyimides therefrom. More particularly the invention pertains to a process which comprises effecting reaction at elevated temperatures be tween trimellitic anhydride (which term by definition is intended to include trimellitic acid) and a member selected from the class consisting of polyols (which by definition is intended to include polyethiols) and a disecondary amine whereby water is removed at the elevated temperatures to effect formation of a composition corresponding to the formula where Z is a member of the class consisting of oxygen, sulfur, and the etc.) etc.] where R is a monovalent aliphatic hydrocarbon radical.

U.S. Patent 3,183,248 describes the preparation of esters of trimellitic anhydride corresponding to Formula I Where Z is oxygen and Q is derived from dihydroxy aliphatic hydrocarbons preferably containing from 2 to 12 carbon atoms. In accordance with this patent trimellitic anhydride is reacted with ethylene glycol diacetate and the reaction mixture heated at elevated temperatures to evolve acetic acid and to form the desired ester of trimellitic anhydride. There are several disadvantages in employing this process for making the esters of trimellitic anhydride. In the first place, it is necessary to convert one of the reactants to the acetate which obviously injects an extra step and adds to the cost of making the ester of trimellitic anhydride. In addition, the time of reaction whereby acetic acid is removed to form the desired ester is exceedingly long and according to the example varies from about 12 to 16 hours. Furthermore, the evolution of acidic acid requires precautions as to the corrosiveness of the acid.

British Patent 1,019,568 describes a class of hardeners for epoxy resins in which the hardeners are tetracid adducts of trimellitic anhydride formed from the reaction of a dihydroxy aliphatic hydrocarbon, such as diethylene glycol, etc., by reacting the diol with trimellitic anhydride. However, in this reaction, the reactants are heated at a temperature and for a time required only to form the tetracid. There is no indication in this patent that the formation of the dianhydride of Formula I is caused or even contemplated. From the objective of this patent directed to making the tetracid adduct, water is not a byproduct of the reaction if one is to obtain the tetracid.

Unexpectedly I have discovered that I can prepare dianhydrides of Formula I by effecting reaction between trimellitic anhydride and a glycol or a disecondary amine directly whereby heating at a sufiicientlly high temperature to remove water, yields not the tetracid as in the aboveidentified British Patent 1,019,568, but rather one obtains unexpectedly an intermolecular transesterification to give the dianhydride of Formula I.

The esters (including the thiol esters) and amides of trimellitic anhydride formed by my process hav many uses. Thus, they can be used to effect curing of epoxy resins to the substantially infusible and insoluble state; such compositions are especially useful as casting compositions for electrical motors, etc. In addition, these dianhydrides can be reacted with primary diamines such as mphenylenediamine, ethylenediamine, trimethylenediamine, o, m, or p-xylylenediamine, 4,4'-oxydianiline, 4,4'-methylenedianiline, etc. in the manner described in British Patent 570,858 and in U.S. Patent 3,277,043 issued Oct. 4, 1966, to form polyamide acid resins which can be converted by heat to high temperature polyimides useful as insulation for electrical conductors, as dipping varnishes to impregnate coils of previously insulated Wire, for example, in motor generator rotors, field coils, etc.; as molding resins, advantageously employing various fillers; for preparing fibers, as impregnants in bonding materials for metallic and fibrous laminates, etc. The polyamide films are suitable as a dielectric for making capacitors, as slot insulation in motors, etc.

Although the process whereby the intermolecular transesterification takes place is not clearly understood, it is believed that there is selective reaction to form the dianhydride by the elimination of water. Initially, it is believed that the reaction between the trimellitic anhydride and the polyol or disecondary amine yields a tetracid corresponding to the formula Z Q Z 'i H000 -000H I-IOOC 00011 and thereafter molecules of this latter formula interact with each other with the elimination of Water and intraversion to form the dianhydride of Formula I, where Z and Q have the meaning given above. In the practice of my invention, it is essential that the temperature be high enough and the reaction be carried out under such conditions that Water is eliminated up to the maximum or stoichiometric amount possible by the reaction indicating formation of the dianhydride. By employing my process, one avoids the necessity of making any derivatives of the reactants such as in the aforementioned U.S. Patent 3,183,248 and one does not have to deal with any corrosive by-product such as acetic acid. In addition, if the proper temperature conditions are employed at which water of esterification is removed, the reaction takes place in a relatively short period of time of the order of from to 120 minutes at most. The reaction embraced by my process goes essentially to completion so that minimum clean up of the reaction mixture is required to isolate the desired dianhydride.

Among the glycols which may be employed in the practice of the present invention are preferably those having from 2 to 12 carbon atoms and may be wholly aliphatic or may have aromatic substituents therein. Included among such polyols containing terminal hydroxyl groups are the glycols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,12-dodecanediol, thioglycol (HS-CH CH SH), other polythiols corresponding to the various hydroxy terminated compounds recited above; polyols containing other hydrocarbon units such as aromatic units, for example, p-xylylene-a,a'-diol, etc.; mixed thioglycols, i.e., those containing both a hydroxy group and a thio alcohol group, for example,

etc.; glycol ethers, for instance, diethylene glycol, triethyleneglycol, etc. Included among the disecondary amines are those, for instance, of the formula R R H1 IQI IH where Q has the meaning given above and R is a monovalent aliphatic hydrocarbon radical (e.g., alkyl, for instance, methyl, ethyl, propyl, isobutyl, etc.; aralkyl, e.g., benzyl, phenylethyl, etc.; alkenyl, e.g., vinyl, allyl, etc.), examples of which are, for,instance, N,N-dimethylethylene diamine, N,N'-dibenzylethylene diamine, N,N-dibutyl butylene diamine, N-methyl-N'-ethylethylene diamine, N,N-diallyl propylene diamine, N,N-diethylpropylene diamine, N,N-dimethyl-m-phenylene diamine, etc. Disecondary amines containing nitrogen in a ring, e.g., piperazine are also included. Alkane polyols containing three or more hydroxyl groups as, for instance, glycerol, trimethylol propane, pentaerythritol, etc., can also be used in an amount up to 25 mol percent replacement of the diols. Additionally, it should be understood that mixed hydroxyamine derivatives containing an aliphatic substituted hydroxyl group and a monosecondary amine group (hereinafter identified as alkanolamine) can be employed as, for instance, N-methylethanolamine, N-ethylpropanolamine, etc.

Generally, the reaction can be carried out by direct transesterification of the trimellitic anhydride and the polyol or amine derivative. However, the use of solvents inert to the reactant and reaction product, such as biphenyl, diphenyl ether, chlorinated aromatic hydrocarbons, are not precluded as long as the boiling point of the solvent, whether at atmospheric pressure or under superatmospheric pressure is maintained at a sufficiently high temperature to remove the water of esterification as it is formed.

Generally, one employs a molar ratio of at least two moles of the trimellitic anhydride (or trimellitic acid) to about one mole of the glycol or disecondary amine reactant. The use of a molar excess of the anhydride is not precluded and it is not critical as to what molar concentrations are employed as long as the molar concentration used is that designed to give optimum formation and yield of the desired trimellitic anhydride derivative.

The temperature of reaction is generally not critical as long as the temperature used is sufficient to effect removal of the water of esterification. Generally, this will encompass temperatures of the order of about 230300 C. or more. Obviously, the temperature employed will determine the rate of removal of the water and as higher temperatures are used, the time for removal of water will be shortened. It is also important that the water be removed from the reaction zone as it is formed in order to avoid hydrolysis of any formed anhydride product.

In order that those skilled in the art may better understand how the present invention may be practiced, the

4 following examples are given by way of illustration and not by way of limitation.

Example 1 as evidenced by the following analyses:

Percent calculated: C, 58.4; H, 2.5. Found: C, 58.5; H,2.5.

Example 2 A mixture of 19.2 grams (0.1 mole) trimellitic anhydride and 6.9 grams of p-xylylene-a,ot-diol (0.05 mole) was reacted in a vessel with stirring for about 15 minutes while the temperature was raised during this period gradually from 225-290 C. During all this time, water of esterification was removed until 1.7 grams water had been obtained (1.8 grams theoretical). The solid product thus obtained melted within the range of 69-75 C. This product was identified as having the formula as evidenced by the following analyses:

Percent calculated: C, 64.0; H, 3.1. Found: C, 62.4; H, 3.2.

Example 3 A mixture of 76.8 grams (0.4 mole) trimellitic anhydride and 17.2 grams (0.2 mole) piperazine was caused to react with stirring for 15 minutes while the temperature was raised gradually during this period from 200- 300 C., at the same time removing 7.1 grams of water (7.2 grams theoretical). On cooling, a product having the formula was obtained. This structure was confirmed by the following analyses:

Percent calculated: C, 60.8; H, 3.24; N, 6.5. Found: C, 59.3; H, 3.47; N, 6.6.

Example 4 In this example, 192.13 grams (1.0 mole) trimellitic anhydride, and 64.5 grams (0.5 mole) neopentyl glycol were mixed with stirring and heated for a period of about minutes during which time the temperature was raised gradually from C. to 300 C. while simultaneously removing a total of 17.7 grams water (18.0

grams theoretical). The product thus obtained had a melting point of 76-78 C. Analysis of the composition showed it to have the structure as evidenced by the following elemental analyses:

Percent calculated: C, 61.2; H, 3.5. Found: C, 60.5; H. 3.9.

Example A thioglycolate ester of trimellitic anhydride having the formula o o H was prepared by elfecting reaction at elevated temperatures between 408 grams (2.13 moles) trirnellitic anhydride and 100 grams (1.06 moles) dithioglycol (1,2- ethanedithiol) employing the same conditions as in Example 1 to give the above thiol ester.

Example 6 Into a reaction vessel equipped with stirrer and nitrogen stream were charged 76.8 grams (0.4 mole) trimellitic anhydride and 21.2 grams (0.2 mole) diethylene glycol. The mixture was heated until molten at 178 C. and thereafter further heating caused the pot temperature to rise to 250 C. before any evolution of water was noted. The nitrogen stream was passed through the reaction vessel to assist in the removal of water efliuent while the temperature of the reaction vessel was raised progressively to 262 C. The heating was continued for about 60 minutes to yield 86.8 grams (96% yield) of a trimellitate having the formula C ll 0 The identity of this composition was established as evidenced by the following analyses:

Percent calculated: C, 58.2; H, 3.1. Found: C, 57.2; H, 3.4.

The following example illustrates the preparation of an ethylene glycol-bis-trimellitate in which 10 mole percent of ethylene glycol is replaced by glycerine.

Example 7 In this example 96 grams (0.5 mole) trimellitic anhydride, 13.95 grams (0.225 mole) ethylene glycol, and 2.2 grams (0.025 mole) glycerine were added to a reaction vessel and the mixture stirred and heated for minutes while progressively raising the temperature from 225 to 300 C. This heating was carried out while simultaneously removing about 7 grams of water (7.2 gram theoretical). This ethylene glycol-glyceryl-bis-trimellitate was then formed into a solution by adding the reaction mixture to 378 grams of a mixture of o,p-cresol at 190 C., cooling the solution thus formed to 90 C., and adding 50 grams (0.253 mole) p,p'-methylene dianiline. The mixture was then heated gently at about 45 to 55 C. for 15 minutes to give a polyamide acid ester solution which had an mtrinsic viscosity of about 0.11. A film was made by casting a portion of this solution on an aluminum plate, and heating at from to 300 *C. progressively to give a tough, flexible, film which had a cut-through temperature of 330 C. as measured by the method described in US. 2,936,296, issued May 10, 1960.

Example 8 This example illustrates the effect of reacting trimellitic anhydride with a polyol under conditions where water is not removed. More particularly, 76.8 grams (0.4 mole) trimellitic anhydride was heated until it was molten and then cooled to around C. at which time 12.4 grams (0.2 mole) ethylene glycol was added rapidly and the mixture stirred to give a crystalline product having a melting point of 215-220 C. This composition was identified as having the formula HOOC OOOH HOOG- COOI-I as evidenced by the following analyses:

Percent calculated: C, 53.8; H, 3.]. Found: C, 53.1; H, 3 2

Example 9 The composition having the formula Percent calculated: C, 59.5; H, 3.1; N, 3.3. Found: C, 59.9; H, 3.0; N, 3.4.

Example 10 To a reaction vessel equipped with stirrer and distil1ation column furnished with a means for removal of water were charged 76.85 grams (0.4 mole) trimellitic anhydride and 18.81 grams (0.2 mole) 13-mercaptoethanol. The mixture was heated with stirring under nitrogen to a temperature of 230 until water began to evolve. The temperature was then increased gradually over a 20 minute period to 290 C. Thereafter a. vacuum of 10.8 mm. (Hg) was applied to the system while heating for an additional 20 minutes at around this temperature. This 7 yielded a dianhydride product melting at 158160 C. and having the following structure:

The following example illustrates the ability to make the trimellitate ester by starting with trimellitic acid instead of with trimellitic anhydride as was done in the foregoing examples.

Example 11 To a reaction vessel equipped with a stirrer and a distillation column containing means to remove water were charged 84.06 grams (0.4 mole) of trimellitic acid and 12.4 grams (0.2 mole) ethylene glycol. The mixture was heated with stirring under a nitrogen sparge at a progressively increasing temperature of from 110 to 210 C. while at the same time removing about 7.2 grams of water. The temperature was gradually increased to 290 C. over a 30 minute period during which time an additional 7.0 grams (theoretical 7.2 grams) of water was collected. A vacuum was introduced into the system at about 0.8 to 1.2 mm. mercury and the reaction product heated at 255-280 C. for about 15 minutes. This product was dissolved in acetone, filtered and the acetone solution separated and evaporated leaving a white solid melting at about 156158 C. This material was found to have the same structure as in Example 1 as shown by the following analyses:

Percent Calculated: C, 58.4; H, 2.50. Found: C, 58.1; H, 2.6.

The following examples illustrate the curing of epoxy resins and the preparation of polyamide acid resins and in turn polyimides obtained from the trimellitate anhydrides prepared above. Cut-through temperatures were determined by the method described in US. Patent 2,936,296.

Example 12 To a reaction vessel flushed with nitrogen were charged 36.2 grams N-methyl pyrrolidone, 4.0 grams (0.02 mole) p,p'-methylene dianiline and 8.2 grams (0.02 mole) of the trimellitate of Example 1. The reaction mixture was heated for a short period of time at about 2550 C. to give a polyamide acid of about 25% solids in the N- methyl pyrrolidone solvent. Films cast on a glass surface from this solution were then heated at 100 C. for one hour, at 150 C. for one hour, and at 225 C. for one hour. The polyimide films thus obtained were flexible and had a cut-through temperature of 280 C.

Example 13 A liquid coating solution was prepared by dissolving 5.6 grams of the ester dianhydride prepared in Example 1 and grams of an epoxy resin (Epon 828) in acetone to approximately 50% solids. The liquid coating was applied to a glass panel which was then heated for one hour at 150 C. to yield a cured film which was extremely flexible and had a cut-through temperature of 365 C.

Example 14 A polyimide resin was prepared by charging a reaction vessel with 22.5 grams p,p'-methylene dianiline, 220.5 grams N-methyl pyrrolidone and 57 grams of the trimellitate of Example 4. The reaction mixture was heated gently at about 55 to 60 C. for about 15 minutes to give a polyamide acid resin of about 25% solids. A film was prepared therefrom by casting a portion of the solution on a glass plate and heating the film for one hour at 100 C., one hour at 150 C., and one hour at 200 C. to give a polyimide film which was extremely flexible and had a cut-through temperature of 200 C.

Example 15 A liquid coating solution was prepared by dissolving 6.16 grams of the trimellitate of Example 4 and 10 grams of an epoxy resin (Epon 828) in acetone to approximately 50% solids. The liquid coating solution was applied to a glass panel and cured at 150 C. for one hour to yield a cured film which was quite flexible and had a cut-through temperature of 365 C.

Example 16 A polyamide acid resin was prepared by charging a reaction vessel with 6.34 grams of p,p-rnethylene dianiline, grams N-methyl pyrrolidone, and 13.6 grams of the trimellitate of Example 6. The mixture was heated gently at about 45 to 55 C. for about 15 minutes with stirring to give a polyamide acid resin of about 20% solids. Films were cast from this solution on a glass plate and then heated at C. for one hour, 150 C. -for one hour, and at 200 C. for one hour to give a polyimide film which had a cut-through temperature of C.

Example 17 A liquid coating composition was prepared by dissolving 5.6 grams of the trimellitate of Example 6 and 10 grams of an epoxy resin (Epon 828) in acetone to approximately 50% solids. The liquid coating was applied to a glass panel and heated at C. for one hour to give a cured film which was flexible and had a cut-through temperature of 350 C.

The process of the present invention is capable of preparing a number of compositions some of which have already been described above. In addition to those previously described, a number of other compositions can be described generically as having the formula where Z is a member of the class consisting of oxygen and radical, where R and Q have the meanings given above. The methods and ingredients used to prepare these compositions are described previously.

It will also be apparent that in addition to polyamide acid resins described above prepared from the many trimellitic anhydri de compositions obtained in accordance with my process, other polyamide acid resins can be formed from their reaction with a variety of other diamino compounds. These polyamide acid resins in turn can be heated at elevated temperatures above 50 C., and preferably above 200-300 C. or higher to form the polyimide compositions. Generally, the diamino compound reacted with the trimellitic anhy'dride derivatives herein described can be varied widely as long as there are two primary amino groups attached to at least two consecutive carbon atoms. One class of diamino compound which can be employed eifectively is that having the general formula where R is a divalent organic radical containing at least two carbon atoms. R can be a simple aliphatic radical or it can be monocyclic or polycyclic aromatic organic divalent radicals in which the aromatic rings may be aromatic, heterocyclic, bridged radicals wherein the bridge is oxygen, nitrogen, sulfur, silicon, phosphorus, and substituted groups thereof or directly attached rings, for example, biphenylene, naphthalene, etc. The preferred R rings in the diamine are those containing at least 2 carbon atoms, and where R is aromatic contains from 1 to 2 phenylene groups having 6 carbon atoms characterized by benzenoid unsaturation in each ring.

Among the divalent radicals which R may be are, for instance, ethylene, trimethylene, isopropylidene isobutylene, tetramethylene, pentamethylene, phenylene, tolylene, xylylene, biphenylene diphenylene oxide diphenylene sulfone, diphenylene methane, etc., with valences of the arylene radicals being ortho, meta, or para to each other or to connecting bonds between adjacent arylene radicals.

Included among these diamino compounds are, for example, m-phenylene diamine, p-phenylene diamine, ethylene diamine, propylene diamine, butylene diamine, decamethylene diamine, 1,2-bis-(3-aminopropoxy) ethane, 5- methylnonamethylene diamine,

etc.; hexamethylene diamine, 4,4'-diamino-dipheny1 propane; 4,4'-diamino-diphenyl methane; 4,4'-diamino-dipheny-larnine; benzidine; 4,4-diamino-diphenyl sulfide; 4, 4'-diamino-diphenyl sulfone; 3,3-diamino-diphenyl sulfone; 4,4'-diamino-diphenyl ether; bis-(4-amino-phenyl) diethyl silane; bis(4-amino-phenyl) phenyl phosphine oxide; bis-(4-amino-phenyl)-N-methylamine; 1,5-diaminonaphthalene; 3,3'-dimethyl-4,4'diamino-biphenyl; 3,3- dimethoxy benzidine; 1,4-bis(p-aminophenoxy) benzene; l,3-bis(p-aminophenoxy) benzene; and mixtures thereof.

A still further class of diamino compositions which can be employed are those having the formula I si where R' has the meanings given above for R and in addition may be other organic radicals, for instance, aryl (e.g., phenyl, biphenylyl, tolyl, ethylphenyl, etc.); alkenyl (e.g., vinyl, allyl, methallyl, etc.), cyanoalkyl (e.g., cyanomethyl, cyanoethyl, cyanobutyl, etc.), etc.; R is a divalent organic, e.g., a hydrocarbon radical, many of which have been identified for R; and m is a whole number equal to at least 1, e.g., 1 to 1000 or more.

Among the aminopolysiloxanes of Formula IV em ployed in the practice of this invention may be mentioned, for instance, 1,3-bis-delta-aminobutyl-tetramethyldisiloxane, 1,3-bis-gamma-aminopropyltetramethyldisiloxane,

in which R has the meaning given above wherein at least two of the R'" groups are substituted with an --NH group and a has a value from 1 to 3, inclusive. These amino-polysiloxanes can be prepared by reducing with hydrogen the corresponding cyano-organopolysiloxane employing at the cyano-organopollysiloxane for the purpose those compounds and methods for preparing those compounds disclosed and claimed in US. Patent 3,185,663 and U8. 3,185,719, both issued May 25, 1965 and assigned to the same assignee as the present invention. Additional directions for making the cyanoalkyl polysiloxanes which can be converted to aminoalkyl polysiloxanes can be found in British Patent 786,020, published Nov. 6, 1957.

I have unexpectedly discovered that the incorporation of diamino compositions of Formula IV for reaction with the dianhydride of Formula I either alone or in the concomitant presence of diamino compounds of Formula III greatly improves the corona resistance of polyimide resins prepared from polyamide acid resins derived from the reaction of the above-described ingredients. Where both silicon-containing diamines and diamines free of silicon are used, significant improvements in corona resistance are realized if the silicon-containing diamino compound, for example, that of Formula IV, is present in amounts ranging from as low as J1 to 25 mole percent of the latter, based on the total molar concentration of the diamino compositions employed for making the polyamide acid resins. The corona resistance imparted by the presence of the silicon containing diamino compounds is many times greater than those of polyimide resins from which the former has been omitted in making these polyimide resins.

The initial reaction between the dianhydride of Formula I and the diamino compound of Formula IV readily takes place at temperatures of from 25 to 100 C. to yield an intermediate polyamide acid resin composed of recurring units of the formula where Z, Q, R", R, m, and n have the meanings above.

The reaction between the diamino compound and the dianhydride of Formula I is advantageously carried out in a suitable solvent. Among such solvents may be mentioned, e.g., dimethyl formamide, N-methyl-Z-pyrrolidone, cresol, dimethyl sulfoxide, etc. In general one employs approximately from 0.9 to 1.1 mols of the diamino compound per mol of the dianhydride and advantageously equimolar concentrations are used. The initial reaction can be carried out at from room temperature to 100 C. to obtain the amido acid derivative of Formula V. Thereafter, the solvent is advantageously removed and the resulting polymer heated at temperatures of from about 150 to 400 C. to efiect cyclization and formation of the imide structure of Formula VI.

It will be apparent to those skilled in the art that other diamino compounds free of silicon of the previously identified Formula I IH ---R'-NH can be employed in conjunction with the reaction between the dianhydride of Formula I and the diamino compounds of Formula IV described above. When such diamino compounds are interreacted with the dianhydride of Formula I and the diamino compound of Formula IV, one will obtain polymers which will additionally have recurring structural units of the formula VII where Z, Q, R and n have the meanings above.

In polyamide acid copolymers containing recurring structural units of Formulas V and VII, the molar concentrations of these units can be varied widely. Generally, these copolymers may contain up to mole percent of units of Formula V. Advantageously, the copolymer comprises from about 2 to 98 mole percent of units III of the Formula V and from 98 to 2 mole percent of units of Formula VII.

The following examples illustrate the preparation of polyamide acid resins (and ultimately polyimide resins) from the diamino compounds of Formula IV.

Example 18 Under a nitrogen sparge was added 30.26 grams of N-methyl pyrrolidone, 8.2 grams (0.02 mole) 4,4'-ethylene-bis-anhydrotrimellitate dianhydride of Example 1, 1.98 grams (0.01 mole) p,p-methylene dianiline, and 2.76 grams (0.01 mole) of 1,3-bis-delta-amino-butyltetrarnethyldisiloxane. The mixture was stirred at room temperature (about 25-30 C.) for 12 hours and then filtered to give a polysiloxane amide ester of about 25% solids in N-methylpyrrolidone solvent. The polysiloxane amide ester was composed of recurring structural units of the formulas where n is a whole number in excess of 1.

13 14 Films were cast on an aluminum surface and werecured Also, the ingredients used to make the polyamide acids by heating at 100 C. for one hour, at 150 C. for one and polyimide resins can be varied widely in order to hour, at 200 C. for one hour, and at 250 C. for about yield a multitude of new and useful resinous compositions. 15 to minutes. The polysiloxane-imide-ester film thus The conditions of reaction can be varied widely in acobtained, which was quite flexible and did not become r cordance with the disclosures and teachings of the forefiuid until about 260 C., had a cut-through temperature 0 going description. of about 145 C., and was composed of recurring struc- The polyamide acid resins herein described can be tural units of the formulas VIII O n and ii i in about equimolar concentrations, where n :is a whole combined with other resinous compositions compatible numbe gr ate tha 1. T e ab e poly mid resin i l therewith, advantageously in the presence of a suit-able form Was testes} fOf corona resistance y determmmg solvent, to give compositions of matter which find use the hours to l f under 1200 volts at 60 cycles/See in many applications described previously. Such mixtures Under such condltlons the film Showed no evldence of can then be heated at elevated temperatures effective in failure after 6000 hours. In contrast to this, when the polyimide of Example 12 was tested inthe same manner, the film failed after 66 hours It should be noted that polyimide state and lnterreaction of the former with other resinous materials. Among the resinous compositions with gg ggt g temphthalate (Mylar film) faded m about which the polyamide acid resins may be blended are, for

Example 19 instance, phenol-formaldehyde resins, including modified versions thereof, such as those modified with polyvinyl acetal resins described in US. 3,307,588; polyethylene causing cyclization of the polyamide acid resin to the To a reaction vessel flushed with nitrogen were added 14.99 grams N-methyl pyrrolidone, 4.1 grams (0.01

mole) of the 4,4tethylenegbisanhydrotrimenitate of terephthalate resins, polyester resins derived from a pluample 1 and 2.76 gramswnl mole) of rality of polyols and dimethyl terephthalate as described amino-butyltetramethyldisiloxane. The mixture was in 2,236,296; POIYbeIIZOXaZOIB T681118, example, stirred for 12 hours at room temperature to yield a polythose descrlbed siloxaneamide-este-r of about 30% solid in Namethyl What I claim as new and desired to secure by Letters pyrrolidone. This polysiloxane amide ester was composed Patent of the United States is: of recurring structural units of the formula 0 II HOOC -iIiO-CH2-OH20-C COOH CH3 CH3 NC C-N-(CH -Si0Si(CH L H g H 24 I I 2 AJ 0 CH OH; 11

where n is a whole number in excess of 1. Films were 1. A polyimide resin composed of recurring units of cast and heated in the same manner as in Example 18 the general formula to give a polysiloxane-imide-ester which was self supwhere Z is a member of the class consisting of oxygen, porting and which was composed solelyof recurring ulf r, nd th structural units of the Formula VIII where n is a whole R number greater than 1. N

It will of course be apparent to those skilled in the l art that in addition to using the trimellitic anhydride, the radlca Q is dlvalent resldue P' from trimellitic acid can be used in its place with equivalent Poly/01S, Polythlols, alkanol' am 1neS and dlseconfllary results. Also, other polyols and disecondary amines can amines, R a monovalent allphatlc'hydl'ocarhon radlcal, be employed in place of those recited in the foregoing 15 a dlvalent hydrocarbcn Tadlcal, 15 11 1110110- examples to yield numerous other trimellitic derivatives. 7 valent hydrocarbon or cyanoalkyl radical, m is a Whole number of at least 1, and n is a whole number in excess of 1.

the class consisting of (A) a polyamide acid resin composed of recurring structural units of the formula 2. A polyimide resin composed of intercondensed rewhere Z is a member of the class consisting of oxygen, sulfur, and the radical, Q is a divalent organic residue derived from polyols, polythiols, alkanol amines, and disecondary amines, R is a monovalent aliphatic hydrocarbon radical, R is adivalent organic radical containing at least two carbon atoms and R" is a divalent hydrocarbon radical, R is a monovalent organic radical, m is a whole number of at least 1, and 'n is a whole number greater than 1, the units of formula (a) comprising from 2 to 98 mole percent of the total units (a) and (b).

3. A polyimide resin composed of recurring structural units of the formula 0 C u u and (B) a polyamide acid resin composed of recurring structural units of both (A) and recurring structural units of the formula where Z is a member of the class consisting of oxygen, sulfur, and the radical, Q is a divalent organic residue derived from polyols, polythiols, alkanol amines and disecondary amines, R is a monovalent aliphatic hydrocarbon radical, R is a divalent organic radical containing at least two carbon atoms free of silicon, R" is a divalent hydrocarbon radical, R' is a monovalent organic radical selected from the class consisting of monovalent hydrocarbon radicals and cyanoalkyl radicals, m is a whole number o o H H O O n and 55 equal to at least 1, and n is a whole number in excess o 0 t 0 ll i JOCHzCH2O-( l E -N N-(CHr)4SiOSi(CH2)4 where n is a whole number in excess of l.

4. A polyamide acid resin composition selected from HOOC COOH

CH3 CH ll AH, an; .L

75 where n is a whole number in excess of 1.

6. A polyamide acid resin composed of recurring structural units of the formulas where n is a whole number in excess of 1.

7. A polyirnide resin composed of recurring structural 0 units of the formula where n is a Whole number in excess of 1.

References Cited UNITED STATES PATENTS 3,182,073 5/1965 Loncrini 260-3463 3,274,155 9/1966 Saunders et a1. 26046.5 3,325,450 6/1967 Holub 260-46.5 3,355,427 11/1967 Loncrini 260-78 3,360,502 12/1967 Loncrini 26078 DONALD E. CZAJA, Primary Examiner. M. T. MARQUIS, Assistant Examiner.

U.S. Cl. X.R. 

